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š¬ Think about it
Why do brothers and sisters look different, even with the same parents? Because each one gets a fresh mix of instructions from two parents. Let us see how this mixing happens in plants and animals.
What is sexual reproduction?
- Two parents are involved — usually male and female.
- This is easy to see in animals.
- Even flowering plants have male and female parts.
- Some microbes like yeast also have two 'mating types'.
Example:
A flower has male and female parts in one plant, while animals usually have separate male and female parents.
What are gametes and why do they carry half the instructions?
- Each parent makes special reproductive cells called gametes.
- Gametes carry only half of the parent's genetic material.
- When male and female gametes join, they form a complete set.
- So the instructions do not double each generation.
Gametes Make a Complete Set
Each parent
Makes gametes with half the instructions.
↓
Gametes join
Male and female gametes combine.
↓
A new cell with a complete set of instructions
How does sexual reproduction happen in plants?
- Pollen grains in the anther are the male gametes.
- Ovules deep inside the flower are the female gametes.
- Pollen is carried to another flower — this is pollination.
- When gametes combine, it is fertilisation, forming a zygote that becomes a seed.
From Flower to Fruit
Pollination
Pollen is carried to another flower.
↓
Fertilisation
Male and female gametes combine.
↓
Zygote forms
It becomes the seed.
↓
Fleshy part becomes the fruit
How does sexual reproduction happen in animals?
- In animals, gametes are sperm (male) and eggs (female).
- In fish and frogs, fertilisation happens in water.
- In birds and mammals, sperm are deposited inside the female.
- The sperm swim towards the egg, and fertilisation forms a zygote.
How is the developing young given food in birds and mammals?
- In birds, the female lays the fertilised egg.
- The egg holds enough food for the embryo until it hatches.
- In most mammals, the embryo develops inside the female's body.
- The mother's body provides food and oxygen until birth.
Birds (lay eggs)
Most mammals (give birth)
Embryo develops inside the laid egg
Embryo develops inside the female's body
Egg stores food until hatching
Mother's body gives food and oxygen
Important Points
- Sexual reproduction needs two parents and their gametes.
- In plants, pollination and fertilisation form a seed.
- The zygote may develop inside or outside the body.
ā Test Yourself
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What are gametes?
View Answer
Special reproductive cells that carry half the parent's genetic material. -
What are the male gametes in a flower?
View Answer
Pollen grains found in the anther. -
What is fertilisation?
View Answer
When male and female gametes combine to form a zygote. -
Where does fertilisation happen in fish?
View Answer
In water. -
How does a bird's egg feed the embryo?
View Answer
The egg holds enough food to last until the chick hatches.
Important Definitions
- Sexual reproduction — reproduction where instructions from two parents combine.
- Gametes — special reproductive cells carrying half the parent's genetic material.
- Pollination — the carrying of pollen from one flower to another.
- Fertilisation — the joining of male and female gametes to form a zygote.
- Zygote — the new cell formed when two gametes combine.
